FILTERS. 45 
temperature of an oven in which bread is baked). ‘The reason for this lies in the fact 
that in three or four days time certain small 
Preoaue 
4D |" 
organisms are able to grow through the 
walls of the filter and make their appear- 
ance in the filtered fluids on the other 
side. Persons who never bake their 
water-filters rest in unwarranted secu- 
rity. The bougies must also be handled 
with great care and inspected carefully 
after each baking for the appearance of 
minute cracks. ‘To detect cracks, im- 
merse the tube in water and. blow into 
it. Clogged filters should be sent to 
the firers of china, where they may be 
purified by heating to dull redness. 
ANIMAL FLuIDs. 
BEEF-BROTH. 
(a) Acid, neutral, and alkaline. 
(4) The same, with addition of 0.5 
per cent c. p. sodium chloride and 1 per 
cent peptone (Witte’s peptonum siccum, 
Merck’s brown peptone, Savory & 
Moore’s brown peptone, etc.). This is 
ordinary peptonized beef-broth. 
Examine as in case of plant juices. 
The term peptone, as it occurs in bac- 
teriological literature, usually means 
commercial peptone, which is a mix- 
ture of true peptone and various pro- 
teoses or albumoses. It is therefore 
generally best to specify just what pep- 
tone is used. The writer now gen- 
erally uses Witte’s dry white peptone. 
Savory & Moore’s brown peptone from 
flesh is very good for some purposes. 
*Fic. 41.—Dr. Roux’s pressure-filter, made by Maison Wiesnegg (P. Lequeux), Paris. The 
working capacity of this filter is about 1.3 liters. The principal parts are: A, tube for connection 
with compressed-air system; B, cut-off; C, cover held in place by strong bolts; D, central reser- 
voir; E, cut-off; F, screw collar which holds the bougie in place; G, heavy metal cylinder surround- 
ing the bougie; H, cut-off, which is closed of course when the apparatus is in use; I, funnel 
through which G and D are filled; K, device for ster 
ilizing the interior of the apparatus. by steam 
under light pressure (it consists of a copper chamber partly full of distilled water, to the bottom 
of which the Bunsen flame is applied; the chamber 
may be unscrewed and removed); L, button 
which is unscrewed to fill the chamber with water (in its center is a steam safety valve acting 
under feeble pressure); M, valve which cuts the steam-generator out of the general circulation 
when fluids are being filtered; N, tripod-top on which the apparatus turns freely. Height, 33 inches. 
